visualization of fuel cell water transport and ... · cd (a/cm2) hfr (Ω cm2) 3-channel, 15-pass...
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Visualization of Fuel Cell Water Transport and Characterization under Freezing Conditions
Project Sponsored by: Department of Energy
Satish Kandlikar, RITThomas Trabold, GM
Jeffrey Allen, MTU
February 13, 2007
This presentation does not contain any proprietary or confidential information.
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Water Management Issues, PEMFC
Excessive Water-Block reaction sites -Saturate diffusion media -Clog gas channels
Zhang et al., 2006. Yamada et al., 2006.
Insufficient Water - Reduced Membrane proton
conductivity - Membrane fracture and failure
http://www.psrc.usm.edu/mauritz/images/nafion2b.jpg
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Repeated Freeze/Thaw Cycles -Damage can be done to all components of PEMFC
Before After 3 freeze-thaw cycles
Water Management Issues, PEMFC
- structural damage to GDL - Loss of surface characteristics - Loss of cell performance
Preliminary images of a GDL sample after several freeze-thaw cycles, RIT
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Project Focus:From Fundamentals toComponent-level research
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3 year, $3.5 Million ProgramVisualization of Fuel Cell Water Transport and
Performance Characterization
Deliverables
Collaborative Research
Incr
easi
ng R
esis
tanc
e
Gas Diffusion Layer Structure Two-Phase Flow in GDL / Channel Interface
Participants
Impact • low-cost, robust systems
• faster commercialization
• US technological leadership in fuel cell industry
technical leadership of
Incr
easi
ng R
esis
tanc
e
Gas Diffusion Layer StructureTwo-Phase Flow in GDL / Channel Interface
Participants
3 year, $3.5 Million Program Visualization of Fuel Cell Water Transport and
Performance Characterization
Optimized materials, design features and operating parameters under normal & freezing conditions
Impact
Deliverables
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Project Flow – Iterative research, learning and performance improvement
Parametric Studies at Component Level
Assessment on Ex-situ Apparatus
In-situ Combinatorial Performance
Definition Baseline Performance
Is performance Improved over baseline?
?
?
No Yes
No
Is performance further improved over baseline?
In-situ Performance with
Current Density Measurements
channel properties
Final Recommendations
?No
Is water distribution acceptable for overall and freeze-thaw operation?
Yes
Task 3
Task 4 Implement Changes, Combinatorial
Task 5
Baseline System Task 2
Characterization
Task 1
Task 6
Water Distribution and
Spatially vary GDL and/or
Task 7
Yes
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Collaborative Research PlanRochester Institute of Technology, P.I.
Professor Satish Kandlikar -Significant experience in fundamentals of two-phase and microchannel flows, high speed imaging, modeling Professor N. Rao -Infrared imaging and digital video image processing
General Motors Dr. Thomas Trabold, Jon Owejan -The forefront of automotive fuel cell technology -Extensive research & development facility
Michigan Technological UniversityProfessor Jeffrey Allen -Expertise in two-phase capillary-driven flows in channels and porous media
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Collaborative Research:From fundamentals to applications
-Component level to stack
Iterative Understanding-Studying the many fundamental processes
-Combine fundamentals into more complex experiments
Novel Techniques-Infrared Visualization
-High-Speed Visualization
-Neutron Radiography
-3-D Microscopy
-Eventually reach complete optimization of PEMFC
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Experiments and Modeling
• Ex-situ experiments – water transport at GDL/channel interface, single-channel and multichannel two phase flows, header effects, freeze-thaw effects, modeling of pressure drop andinstabilities.
• In-situ experiments – Direct visualization, local water holdup, local current distribution and freeze-thaw effects atcomponent level using neutron radiography, verification of models.
• Post-mortem analysis – Microscopic analysis of GDL samples to study freeze-thaw effects as a function of cycling and shut-down protocol.
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1. 14.6 m2 (157 ft2) floor space NIST-GM jointly 2. Variable L/d ratio
3. Current support for fuel cell developed fuel cell experimentsimaging facility • Hydrogen flow rates
18.8 lpm• micro fuel cell controller
with 3 lpm H2 flow rates • Portable Current
Distribution Board
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Visualization studies
• High speed imaging • GDL/channel studies • Single-channel, multiple channel and header flows • Flow patterns, instabilities and pressure drop
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Optimized GDL/Bipolar Plate Combination
GDL to channel transport Two-phase flow within channels
and diffusion media Surface energy of diffusion media
and plates Channel geometry & manifold
design Optimize channel and manifold
design for performance, voltage stability and freeze
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In
Out
P = 200 kPa, T = 80 C
A/C RH = 42/25%
CD (A/cm2) HFR (Ω cm2)
3-channel, 15-pass serpentine cathode
D = 0.5 mm; Land: W = 0.7 mm
Current Density = 0.2 A/cm2
Cell Voltage = 0.803 V Cell HFR = 0.095 Ω cm2
high local HFR,
current to well hydrated outlet
region.
100 square segments Inlet dry condition
A/C Stoich = 2/2
Current density and HFR distributions
Channel: W = 0.9 mm,
Dry inlets produce
resulting in shift of
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Optimized Water Distribution
Optimized Water Distribution
Crucial to obtaining high performance and long life
Mitigate dryout at inlets and water accumulation at outlets
Minimize freeze start time and energy
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Thank You!